216 



Male somewhat smaller than female, but scarcely differing from it in the 

 general shape of the shell. Copulative appendages of comparatively small 

 size and simple structure, basal part rounded quadrangular in shape, with only 

 a few chitinous thickenings and a small pointed process below; terminal part 

 abruptly recurved, having the form of a thin falcate lamella. 



Colour of shell dark violaceous brown. 



Length of adult female 0.62 mm. 



Remarks. The. present form differs notably from those described in the 

 preceding pages in the shape and structure of the shell, and should perhaps 

 more properly be included in a particular genus together with the succeeding 

 species to which it is evidently closely allied. 



Occurrence. I have only met with this form in a single locality, viz., in 

 the 0stnaes Fjord, at the Lofoten islands, where a few specimens were taken 

 in a depth of 6 12 fathoms, sandy bottom. 



Distribution. British Isles, Arctic Sea; Spitzbergen, Baffins Bay. 



Fossil: Norway, British Isles. 



112. Cytherura cellulosa, (Norman). 

 (Pi, c, fig. 2). 



Cythere cellulosa, Norman. Nat. Hist. Trans. Northumb. & Durham, Vol. I, p. 22, 

 PI. V, figs. 1720, PI. VI, fig. 17. 



Syn: Cytherura nana, G. O. Sars. 



Specific Characters. Female. Shell much compressed, seen laterally, oval 

 subrhomboid in shape, greatest height in the middle and about equal to 3 /5 

 of the length, dorsal margin well arched throughout, ventral nearly straight 

 and terminating behind in a blunt corner, anterior extremity obliquely rounded, 

 with the edge divided below into 5 blunt tooth-like projections, posterior 

 extremity obliquely truncated below and produced somewhat above the middle 

 to a blunt protuberance; seen dorsally, narrow oblong in outline, the greatest 

 width scarcely exceeding V 3 of the length, side-edges straight and parallel in 

 the middle, both extremities pointed, the posterior somewhat more abruptly 

 contracted than the anterior. Valves, as in the preceding species, very unequal 

 and dissimilar in shape, surface however quite evenly convex, without any 

 projecting ribs, but marked with a number of irregular rounded areolae of 

 of unequal size, each containing in the middle a little knob-shaped tubercle; inner 

 duplicatures, as in the preceding species, simply emarginate. Anterior antennae 

 somewhat less slender than in the said species, with the terminal joint rathei 



